1. Field of the Invention
The present invention relates to highly fluid-tight device-cable assemblies in which an electric/electronic device and a cable are integrally molded with a resin.
2. Description of Related Art
In order to prevent failure of an electric/electronic device due to the infiltration of moisture or other fluids, device-cable assemblies are widely used in which an electric/electronic device (such as a sensor, a circuit board, and a terminal) and a cable (to which the electric/electronic device is connected) are integrally molded with a resin. For example, an ABS (anti-lock brake system) sensor for vehicle use includes: a sensor for detecting the rotation rate of the vehicle's wheel; and a cable for transmitting signals from the ABS sensor. Such an ABS sensor is mounted near a vehicle's wheel, and is therefore required to withstand harsh conditions such as deposition of water or ice and a wide temperature range from −40° C. to 150° C. In view of these circumstances, in order to achieve higher fluid-tightness, sensor-cable assemblies in which a sensor and a cable are integrally molded with a resin are employed (see, e.g., JP-A 2005-172687).
Cables for use in such ABS sensor-cable assemblies need to be flexible and thermally resistant. So, the sheaths of such cables are often made of a fluorocarbon-based polymer or a modified fluorocarbon-based polymer, which is thermally resistant up to 200° C. and is also flexible. In addition, in such ABS sensor-cable assemblies, in order to prevent moisture from infiltrating into the sensor, the fluid-tightness between the cable and the molded resin needs to be sufficiently high.
However, when a fluorocarbon-based polymer or a modified fluorocarbon-based polymer is used as the cable sheath material, it is often difficult to achieve a sufficiently high fluid-tightness between the cable of such a sensor-cable assembly (which is integrally covered with a molded resin) and the molded resin. The general explanation for this difficulty is as follows: Generally, fluorine atoms and carbon atoms strongly bind together, and therefore the surfaces of fluorocarbon-based polymers are nonadherent (i.e., it is often difficult for other materials to adhere to the surfaces of fluorocarbon-based polymers). Furthermore, fluorocarbon-based polymers do not or are not sufficiently molten even at a temperature as high as the molding temperature of the resin.
In order to solve the above problem and facilitate adherence, printing or painting to fluorocarbon-based polymers, there are proposed methods for modifying the surface of a fluorocarbon-based polymer by blowing, toward the surface, a flame of a fuel gas containing a modifying compound (see, e.g., JP-B 3557194 and JP-B 4050787). For the purpose of covering cables, various resins for molding are used. However, it is not ensured that all of such various molded resins adhere well to the surface of a cable modified by the above-mentioned surface modifying treatment.